Well said. Maybe it does not work at near-stall, like Gordy flies, but for slope racing, it works very well. I set up all my planes to be right at neutral or slight tuck when put into a steep high speed dive. This way they all fly the same, and their response is ideal for racing conditions. The CG setting can be confirmed by flying inverted and noting that little down stick is required.
Bill DelHagen [EMAIL PROTECTED] >From: "Scobie Puchtler or Sarah Felstiner" <[EMAIL PROTECTED]> >To: <[EMAIL PROTECTED]>, "RCSE" <[EMAIL PROTECTED]> >Subject: [RCSE] More Dive test talk: some clarification? >Date: Thu, 3 Apr 2003 07:45:26 -0800 > >Rense, and all, >there may be a communication problem in this >thread, in that folks are comparing the Dive Test >to procedures used to set up a glider for a >specific recommended flight behavior >(CG-Decalage-trim setup). > >The Dive Test is simply a diagnostic tool for >determining just where along the pitch stability >spectrum a given glider is set up. By itself, it >is NOT a method of achieving any one particular >kind of CG/decalage/trim setup. To use the Dive >Test as a tool for achieving a particular >CG/decalage/trim setup, you have to know in >advance what kind of pitch stability condition you >want to fly (slightly positive? strongly positive? >very close to neutral? truly neutral?) Once you >know what your goal is along the pitch stability >spectrum, the dive test becomes a very elegant >method to see if you have achieved that particular >condition. > >The vast majority of RC glider pilots, whether >they know it or not, like to fly with slight >positive stability (some want a little more and >some want less, perhaps riding the hairy edge of >truly neutral stability), and it sounds like you, >Rense, are no exception. This condition of slight >positive stability shows up in the dive test as >gradually pitching up, or 'recovering' from the >dive with no control input. If you have more >positive stability, the recovery will be sharper; >with less, it will be more subtle. The speed or >downward angle of the dive test is relatively >inconsequential. If your dive test angle is gentle >enough, you may barely be able to see this >'recovery', but if your glider has slight positive >stability, the recovery WILL be there nonetheless. >If the downward angle of your dive is a bit more >dramatic, then the steady pitch recovery will be >more visually obvious. > >Unfortunately the name "Dive Test" can be >misleading. It has nothing to do with 'testing the >dive' of your glider. It is testing the pitch >stability condition of your glider by observing >it's reaction to accelerated flight without >control inputs. The 'dive' part of the test is >just a convenient, relatively safe way (given >appropriate altitude) to get the acceleration >necessary for the diagnosis. (Calling it the >"Reaction to Accellerated Flight w/o Control >Inputs Test" would be a bit awkward) > >There is nothing particularly wrong with getting >to your preferred set up by another method, and >certainly almost any glider pilot would want to >make sure that a plane is basically flyable and >maneuverable with gentle test glides near the >ground, maybe even with some tall grass as a nice >cushion. > >The elegant thing about the Dive Test is that it >is simple, definitive, does not discriminate >between types or tasks, and it never assumes that >you want any one particular result. Instead it >simply shows you exactly where your current setup >falls along the pitch stability spectrum. If you >understand the relationship of CG/Decalage/trim >and pitch stability, it takes ALL the mystery out >of what to change in order to get just the results >you're looking for. It is a universal measure of >pitch stability for all gliders from the lightest >floater, to the most heavily-leaded slope missile, >because it reflects the fundamentals of how >gliders function. > >So, if you mostly fly one kind of plane and one >kind of task, and you have a way to achieve the >CG-decalage-trim setup for your plane(s) that is >reliable and gets you what you want, then the Dive >Test may feel unnecessary to you. But if you fly >all kinds of gliders in all kinds of conditions, >and you want a non-mysterious way to be in control >of setting up the CG-decalage-trim for ANY glider, >or changing that setup to get a very specific, >predictable, and desired change in pitch handling >and reaction to lift, then a simple, clear >understanding of the CG-decalage-trim relationship >coupled with an appropriately applied Dive Test is >darn hard to beat. > >Lift, >Scobie in Seattle > > > > > > > > > This is something we can all just try > > next time we're out flying (i.e., > > observing whether speed changes the > > dive test, but intuition says its > > true). Also, the handtoss method > > depends clearly on how fast the plane > > is thrown (hence the requirement that > > only the last part be considered). My > > handtoss aligned planes ended up > > pulling out of a dive slowly but > > surely. So, perhaps the results of the > > two methods don't differ all that much > > in the end. > > > > Rense > > > > -------Original Message------- > > From: Scobie Puchtler or Sarah > > Felstiner <[EMAIL PROTECTED]> > > Sent: 04/02/03 12:38 PM > > To: [EMAIL PROTECTED], RCSE > > <[EMAIL PROTECTED]> > > Subject: Slow vs. Fast Dive test. > > > > > > > > > But, doesn't it follow from this very > > > logic that things change with > > > variations in speed? So, a slow dive > > > test gives different results than a > > > fast one - always? > > > > Different results?, not really. A slow dive test > > simply gives a less dramatic result than a fast > > one. The basic result will always be the same. > > > > Lift, > > Scobie. > > > > > > > > > > > > > > >RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off.
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